Quick Notes Covalent Bonding

  • A covalent bond is the sharing of one pair of electrons between two atoms.
  • Atoms are most stable when they have a ‘full’ outer shell of electrons.
    • To have access to full outer shells, atoms can ‘share’ electrons between orbitals.
  • Non-metals form covalent bonds with other non-metals.
  • As covalent bonds occur between atoms, they are atomic bonds.

Full Notes Covalent Bonding

Atomic Structure Recap

Atoms have electrons that travel around a nucleus in ‘orbitals’, which can only hold one pair of electrons. These orbitals exist in shells, and each shell is a different distance from the nucleus (1 being the closest, 2 the next closest, etc.).

The most stable configuration for an atom (ignoring transition metals, see Transition Metals) is to have eight electrons in its outermost shell. The reactivity of an element can often be linked to how easily an atom can ‘get' to having eight electrons in its outermost shell. This explains why the noble gases (group 8 in the periodic table) are so unreactive, as they do not want to change their electron number.

With covalent bonding, we are concerned with the outermost electrons and shell of an atom.

In covalent bonding electrons are shared between atoms, giving each atom access to a full outer shell of eight electrons (with the exception being hydrogen, which only wants two electrons).

For example, chlorine atoms have seven electrons in their outer shell. To become stable, they need to gain access to one more electron. Two chlorine atoms are able to come together and share one electron each. Now, each atom has ‘access’ to a full outer shell. This arrangement is called a covalent bond.

covalent bond between two atoms of chlorine sharing electrons a-level chemistry

The group number (one to eight) in the periodic table tells us how many electrons an atom has in its outermost shell, which can tell us how many bonds the atom can make.

For example, carbon is in group 4. This means carbon wants to gain access to another four electrons. Making four covalent bonds with other atoms would give the carbon atom access to a full outer shell. This is why carbon can make four bonds.